2 Answers
2

the original surface was primed, and you didn't use any primer on the patches. Primer seals the surface, so changes how the surface absorbs paint.

the original surface was rolled, and you used a paintbrush. Rollers leave a slight orange-peel texture, whereas a paintbrush -- even the brush you used -- will leave a flat to slightly rippled texture.

You can get small rollers, which might help in matching the texture. Can't really add much else to this answer.
– chrisNov 30 '10 at 23:48

For completeness - you might also not have waited long enough. Sometimes paint takes a day or two to dry to it's final color.
– Joel Spolsky♦Dec 1 '10 at 4:51

1

I second the "mini rollers" idea from chris. I recently removed a small shelf that the previous owners had installed, left some holes that I spackled, sanded and mini rolled. Can't see any differences now that it's dried and set.
– user45Dec 1 '10 at 10:03

The difference you are seeing (like @Niall C. mentioned) is that the area you patched is very smooth from the paint brush but the rest of the wall is speckled from a roller. Possibly you also sanded the wall around the patch job too much and therefore removed the roller pattern that was previously there (making the smooth non-matching area larger and more apparent). Next time when patching a small spot, put on your spackle/joint compound and then you can use a sponge sanding block to remove any high spots (but without sanding too much to remove any of the roller pattern from around the hole). Then you can try and use a paint brush to get a match to the roller pattern by dabbing the area (instead of pulling full strokes) but you would definitely get a matching pattern by using a roller.

@Niall C. mentioned this in his answer but in my opinion priming small areas like you described is not necessary. If this is a larger area (maybe the gouge that you describe, then priming and a roller would be required to get a match).